2-Alkoxyimino-N-carbamoyl-2-cyanoacetamides were disclosed in German Offenlegungsschrift No. P 2312956.8 published Sept. 20, 1973. These compounds are agricultural fungicides particularly suited for control of late blight in tomatoes and potatoes and downy mildew in grapes.
It has been found that 2-alkoxyimino-N-carbamoyl-2-cyanoacetamides require a controlled and acidic pH for optimum chemical stability in dilute spray slurries. Surprisingly, even essentially neutral or mildly alkaline waters give significant losses of these fungicides if the spray solutions are held several hours before spraying and particularly if the spray slurry is warm. It is often desirable to mix the cyanoacetamides with other fungicides, and many commercial fungicide formulations cause significant losses of the cyanoacetamides. The problem is particularly severe with these compounds because they are normally used at very low levels (on the order of 150 ppm) while most companion fungicides are used at rates on the order of 1000 ppm or more. It is remarkable that this instability is noted only in solution. Dry powder formulations, with their normal low levels of moisture are very stable.
This invention provides formulations of 2-alkoxyimino-N-carbamoyl-2-cyanoacetamides which are stable in alkaline spray waters by combining an acidulant with the fungicidal compounds.